Tritiation of stainless steel and cement particles enhances their genotoxic potential

Tritium is a byproduct of nuclear fission activities and permeates in building materials. Decommissioning nuclear power plants could release tritiated steel and cement particles in the environment that could be accidentally inhaled by workers in case of loss of containment. Although tritium is a low energy beta emitter, tritiated particles could remain for years in the lungs after inhalation and subject them to long-term beta radiation. The aim of this study was to advance knowledge in the field of the radiotoxicity of these tritiated particles on human alveolar macrophages, capable of phagocytizing these particles. Although no cytotoxicity was observed, exposure to steel particles induced a significant increase in the production of reactive oxygen species (ROS), whereas exposure to cement particles induced a slight increase of ROS. Despite inducing high oxidative stress, control hydrogenated steel particles did not induce any DNA damage. Control hydrogenated cement particles also induced little DNA damage. DNA damage was higher after particle tritiation. The tritiation led to larger fractions of cells with similar levels of DNA damage, particularly at the lowest concentration. Significant chromosomal damage occurred after exposure to hydrogenated and tritiated particles, but only tritiated particles induced a concentration-dependent response. Overall, our results suggest that hydrogenated particles are moderately genotoxic and the tritiation of the same particles enhances their genotoxic potential, especially increasing their clastogenic potential. The data highlight a specific toxicity of tritiated particles on alveolar macrophages and improves the current knowledge of tritiated particles.